a(n) = n^2*4^n/4.

Terms

a(0) =0a(1) =1a(2) =16a(3) =144a(4) =1024a(5) =6400a(6) =36864a(7) =200704a(8) =1048576a(9) =5308416a(10) =26214400a(11) =126877696a(12) =603979776a(13) =2835349504a(14) =13153337344a(15) =60397977600a(16) =274877906944